SEROEPIDEMIOLOGIC SCREENING OF PIG SERA COLLECTED AT THE SLAUGHTER HOUSE TO DETECT HERDS INFECTED WITH AUJESZKYS DISEASE VIRUS, PORCINE INFLUENZA-VIRUS AND ACTINOBACILLUS (HAEMOPHILUS) PLEUROPNEUMONIAE IN THE FRAMEWORK OF AN INTEGRATED QUALITY-CONTROL (IQC) SYSTEM

Over a period of six months, approximately 4700 blood samples were collected from 97 pig-finishing farms in the provinces of Noord-Brabant and Gelderland and screened for antibodies with respect to Aujeszky's disease virus (ADV), porcine influenza virus (PI) and Actinobacillus (Haemophilus) pleuropneumoniae (App). There were significant differences in the percentages of seropositive pigs between the two provinces, which may be related to the difference in the density of the pig population in the two provinces. In practice, it was possible to perform a reliable sera collecting procedure at the slaughterhouse. No farms remained seronegative with respect to most of the disease agents during the sampling period. There was a high degree of variation in the percentages of seropositive pigs per farm as to most of the disease agents. Evidence was found that animals that were seropositive with respect to ADV were significantly more susceptible to becoming seropositive with respect to App. serotype 2, and vice versa. The same connection was observed for PI serotype H1N1 and PI serotype H3N2. Furthermore, evidence was found that pigs seropositive with respect to PI serotype H1Ni only, or to PI serotype H1N1 and ADV or PI serotype H3N2 show a significant decrease in average daily weight gain compared to pigs that were seronegative.